The present invention relates to a system which performs bus arbitration for access made by a plurality of requesters to a shared resource through a shared bus.
Recently, in a system LSI, it has become important to enable requesters, such as a CPU and a media processing engine, to access a shared resource, such as memory, as many times as required by the system. Where requesters make access to the shared resource, an arbiter which performs arbitration to avoid conflicts is necessary.
The pamphlet of International Publication WO98/12645, for example, discloses a method and apparatus for bus arbitration, in which each requester is permitted to make access a set number of times corresponding to a weight allocated to that requester, thereby enabling performance required by the system to be achieved.
In the conventional bus arbiter, however, a high priority is likely to be assigned to a requester which transfers large amounts of data, such as moving images. That is, in a system LSI, etc., used in the field of multimedia, a CPU is often assigned a lower priority than a media processing engine and the like. Thus, a latency time, occurring when the CPU accesses memory and including a time during which the CPU waits for completion of other requesters' accesses, increases. This results in the problem of decreased real time performance of the system.